Packetisation in optical packet switch fabrics using adaptive timeout values

Hybrid electro-optical packet switches utilize optics in the backplane to switch optical packets from inputs to outputs on electronic line cards. The optical packets are traditionally considerably larger than minimum size IP packets. IP packets entering the switch must be formatted (segmented) and encapsulated in the optical packet format. This process is called packetisation or aggregation. This paper investigates a novel technique for aggregating IP packets into optical packets. When the first segment arrives in an optical packet, a timer is started. The optical packet is marked ready for transmission either because the timer reaches a specific timeout value, or because the optical packet is completely filled with segments. Only two distinct values of the timeout value are used. Which of the two timeout values to use, is selected by 3 different control thresholds. The first threshold level applies to the inter arrival rate at the individual VOQs. The remaining thresholds applies to the optical slot level inter arrival rate at the input and output line cards. If any measurements are beyond a given threshold, the higher timeout value is used. The proposed method can be used to make a trade-off between delay and throughput in hybrid electro-optical packet switching. Furthermore, it is investigated how large a speedup is required in order to provide 100% throughput.